When reporting an issue, please try to reproduce the issue with just Dominos and Dominos_Config running.
Error (400+) on login, on 2 characters only (Monk and Evoker). It happens on any existing or new profile on those characters. Also disabled all mods except dominos.

408x Dominos/bars/actionBar/button.lua:265: invalid option in format' [string "=[C]"]: ? [string "=[C]"]: ? [string "@FrameXML/RestrictedFrames.lua"]:674: in function <FrameXML/RestrictedFrames.lua:673> [string "@FrameXML/RestrictedFrames.lua"]:812: in function CallMethod'
[string " if name == "action" then
self:RunAttribute("UpdateShown")
self:CallMethod("OnActionChanged", value)
end
"]:3: in function <[string " if name == "action" then..."]:1>
[string "=(tail call)"]: ?
[string "=[C]"]: ?
[string "@FrameXML/RestrictedExecution.lua"]:484: in function <FrameXML/RestrictedExecution.lua:447>
[string "=(tail call)"]: ?
[string "@FrameXML/SecureHandlers.lua"]:128: in function <FrameXML/SecureHandlers.lua:121>
[string "=[C]"]: ?
[string "@FrameXML/SecureHandlers.lua"]:266: in function <FrameXML/SecureHandlers.lua:263>
...
[string "@FrameXML/UIParent.lua"]:576: in function UIParentLoadAddOn' [string "@FrameXML/UIParent.lua"]:781: in function MajorFactions_LoadUI'
[string "@Blizzard_ExpansionLandingPage/Blizzard_DragonflightLandingPage.lua"]:179: in function SetUpMajorFactionList' [string "@Blizzard_ExpansionLandingPage/Blizzard_DragonflightLandingPage.lua"]:172: in function RefreshMajorFactionList'
[string "@Blizzard_ExpansionLandingPage/Blizzard_DragonflightLandingPage.lua"]:167: in function RefreshOverlay' [string "@Blizzard_ExpansionLandingPage/Blizzard_DragonflightLandingPage.lua"]:158: in function <...sionLandingPage/Blizzard_DragonflightLandingPage.lua:154> [string "=[C]"]: in function CreateFrame'
[string "@Blizzard_ExpansionLandingPage/Blizzard_DragonflightLandingPage.lua"]:122: in function CreateOverlay' [string "@Blizzard_ExpansionLandingPage/Blizzard_ExpansionLandingPage.lua"]:63: in function RefreshExpansionOverlay'
[string "@Blizzard_ExpansionLandingPage/Blizzard_ExpansionLandingPage.lua"]:35: in function <...pansionLandingPage/Blizzard_ExpansionLandingPage.lua:33>

Addon Version
10.2.7-retail

World of Warcraft Version
10.2.5.53040

Update: I found the issue by looking at line 265 in button.lua. I have a consumable in my bars that I have more than 999 of (1493 to be exact) that is causing this error. Removing it from the action bar and reloading gives no more errors.

Update 2: Quick fix at Line 265, it should be:
self.Count:SetFormattedText("%.1fk", count / 1000)

Yes, this was a typo in my end